Phoenix firefighters rescued a 50-year-old man from a storm drain Monday after he reportedly became trapped and began calling for help from passing students.

A group walking home from school heard the man yelling as they passed the elevated portion of an underground irrigation box on Roeser Road east of Seventh Street, said Capt. Jake Van Hook of the Phoenix Fire Department.

Firefighters saw water in the irrigation box and were able to hear the man, but could not see him, Van Hook said. Other crews began opening nearby manhole covers on Roeser Road and found the man walking through the tunnels.

The man was able to communicate with firefighters and climb out on his own after firefighters lowered a ladder down a manhole, Van Hook said. The man was not injured, he added.

Phoenix police were investigating why he was in the storm drain and how he got there, Van Hook said.